When a telephone subscriber initiates a call, the subscriber's local telephone exchange will enable the routing of the call according to the digits dialled by the subscriber. The local telephone exchange such as a class 5 Switching Point (SP) will select an idle trunk to enable the call to be routed to its destination. The selection of an idle trunk will be made according to whether access to an access tandem is required or whether the call is to be established with another class 5 type telephone exchange.
If a toll call is made, the call can either be routed via an access tandem, or another class 5 type of exchange located outside the originating office's Local Access Transport Area (LATA) depending on the destination Directory Number (DN). If a trunk is congested, the calling party will receive a fast busy tone or recorded announcement. The calling party will then have to re-initiate the call at a later time. This happens quite frequently on special anniversaries such as Mother's Day, New Year's Day, etc.
Recent changes in the way telephone subscribers make use of the telephone network have had an impact on traffic congestion of outgoing trunks of a local telephone exchange. One of these is the offering of promotional long distance rates to telephone subscribers. Long distance service providers will from time to time offer special discounts at certain times of the day to retain or attract customers. In some instances, it was found that customer response to discounted long distance rates is so overwhelming that it has resulted in congestion of a certain of number of outgoing trunks to toll or access tandems during the time the long distance promotion is in effect.
Another network access pattern that has had an impact on traffic congestion on other outgoing trunks has been the enormous popularity of the Internet. Whereas in the past subscribers would remain off-hook for an amount of time of the order of minutes, subscribers connected to the Internet can stay off-hook from tens of minutes to several hours. Thus, the enormous popularity of the Internet as well as the increase in connection time of individual subscribers has had a negative impact on traffic congestion of outgoing trunks from local telephone exchanges.
Unfortunately, along with the success of long distance promotions and Internet access via Internet Service Providers (ISP) telephone network operators have received complaints from residential, business and regular long distance traffic customers as well as those making use of toll free calls using 800 or 888 access and 900 type calls. That is, since all idle trunks can quickly be seized by a telephone exchange during promotional long distance hours, those customers requiring access to outgoing or incoming trunks to make or receive other types of calls can quickly be prevented from accessing the network.
A need therefore exists for a method of alleviating network congestion to minimize the impact on the grade of service of residential, business and regular long distance service subscribers while still being able to offer subscribers access to promotional long distance rates and access to the Internet.